Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$166.92	11.370%	$185.8988	$185.90	$185.90	$185.90
Purchase #2	$133.48	13.493%	$151.4905	$151.49	$151.50	$151.50
Purchase #3	$248.98	13.492%	$282.5724	$282.57	$282.55	$282.60
Purchase #4	$96.91	3.130%	$99.9433	$99.94	$99.95	$99.90
Purchase #5	$16.92	3.487%	$17.51	$17.51	$17.50	$17.50
Purchase #6	$59.75	6.359%	$63.5495	$63.55	$63.55	$63.50
Purchase #7	$162.61	7.397%	$174.6383	$174.64	$174.65	$174.60
7 purchase totals =	$885.57		$975.6028	$975.60	$975.60	$975.50